Background: Breast conserving therapy (lumpectomy [L] and breast radiotherapy [RT]) results in equivalent cancer control outcomes in comparison to mastectomy (M) for early stage breast cancer (BC) based on randomized controlled trials (RCT). Since 2004, RCT support that L alone without RT yields equivalent survival and acceptable local regional outcomes in women ≥70 years old with stage I (T1N0) hormone-sensitive (HS) BC on endocrine therapy. Based on this, we hypothesized that M rates should decrease substantially in this low risk elderly population and sought to examine the influence of race on M rates in this group and how these trends compare to younger aged Stage I HS patients.

Methods: We used the Surveillance Epidemiology and End Results (SEER) registry data to conduct this study. We included women with T1N0 HS BC classified as either ER-positive or PR-positive from 2000-2012 divided into 2 age groups [elderly (≥70 years old) and non-elderly (20-69 years old)] and 3 race groups [white, black, and Asian-Pacific-Islander/American Indian/Alaskan Native (API)]. We compared M rates in women diagnosed before 2004 compared to those diagnosed from 2005-2012. Statistical analyses were performed using differences in proportions (p<0.05 considered statistically significant).

Results: 261,079 women met the study criteria (N=87,009 elderly; N=174,070 non-elderly). In elderly Stage I HS BC, a 5.2% reduction in the M rate is seen: 32.6% before 2004 to 27.4% after 2004 (p<0.0001). M rates remained higher (with less reduction) in elderly Black (30.8 %) and API (33.6 %) vs. White (26.8%) [p<0.0001 for White vs. Black and for White vs. API]. In non-elderly Stage I HS BC, after 2004 M rates increased from 29.2% to 31.8% (p<0.0001). Non-elderly white women had the largest absolute increase in M rates (31.2% vs. 28.5%, p<0.0001) followed by API women (35.1% vs. 37.1%, p=0.0222). M rates did not change after 2004 in non-elderly black women (31.7% vs. 31.7%, p=0.9953).

Conclusions: In patients with favorable stage I HS BC, M rates have decreased only modestly in elderly women since 2004 when L alone w/o RT was established as appropriate treatment. In comparison, M has increased since 2004 in non-elderly women. These trends are driven mostly by white women in both the elderly and non-elderly. Further research is needed to identify why M, which is associated with higher cost and morbidity than L alone, has not changed substantially in elderly very favorable BC, particularly for non-whites.

Citation Format: Bazan JG, Bittoni MA, Fisher JL, White JR. Influence of race and age on mastectomy rates in women with stage I, hormone-sensitive breast cancers: A SEER-based study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-11-05.